CN110763328B - Half-space sound field reconstruction method and device - Google Patents
Half-space sound field reconstruction method and device Download PDFInfo
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Abstract
The invention discloses a half-space sound field reconstruction method and a half-space sound field reconstruction device, wherein the method comprises the following steps: configuring equivalent sources and virtual source surfaces according to the vibrating body and the boundary surface to obtain a plurality of equivalent source configuration schemes; aiming at each equivalent source configuration scheme, calculating a regular solution of a source strong column vector corresponding to each equivalent source configuration scheme based on the predicted sound pressure of the half-space sound field; reconstructing the surface normal vibration speed of the vibrator corresponding to each equivalent source configuration scheme based on the regular solution of the source strong column vector, and further calculating the reconstruction error of the surface normal vibration speed of the vibrator; and finally, the equivalent source configuration scheme with the minimum reconstruction error of the normal vibration speed of the surface of the vibrator is used as a final equivalent source configuration scheme to reconstruct a half-space sound field. The invention utilizes the half-space near-field acoustic holography technology, ensures the reconstruction precision of a half-space sound field by reasonably configuring equivalent sources, does not depend on the surface acoustic impedance of a reflecting surface, and has lower measurement cost.
Description
Technical Field
The invention relates to the technical field of physical acoustics, in particular to a half-space sound field reconstruction method and device based on a half-space near-field acoustic holography technology.
Background
When the vibrating body is located in a half-space sound field environment with a boundary, the influence of the reflection action of the boundary on the sound field is generally considered. The field separation technique can be used to reconstruct a half-space field because it can separate the input sound and the output sound, and has a distinct advantage in that it does not require knowledge of the surface acoustic impedance of the reflecting surface. However, this technique requires that the measuring surface must be a closed surface that envelopes the vibrating body to ensure that the reflected sound propagates into the half-space sound field to be studied just from the other side of the measuring surface. In addition, the sound field separation technology itself has many requirements on the measurement surface, such as double-sided sound pressure measurement or double-sided particle vibration velocity measurement, or single-sided sound pressure-particle vibration velocity measurement. This results in high measurement costs, including economic costs for the measurement equipment and the like and measurement working time costs.
If the surface acoustic impedance of the reflecting surface is known, a half-space Green function can be introduced into the traditional near-field acoustic holography technology to realize reconstruction of a half-space sound field. There are currently two types of semi-spatial green functions: one is based on the assumption of plane waves, and the reflected sound waves are considered to be the plane waves, so that the reconstruction precision of a half-space sound field is obviously reduced when the distance between a vibrating body and a reflecting surface is not far enough; and the other type of the method is based on real spherical waves, automatically meets the boundary conditions of a reflecting surface, can obtain high reconstruction precision of a half-space sound field, and is time-consuming in calculation due to integration. In addition, this method requires a priori knowledge of the acoustic impedance of the reflecting surface, i.e. a dependence on the surface acoustic impedance of the reflecting surface.
There is a technique of half-space near-field acoustic holography that neither requires a priori knowledge of the surface acoustic impedance of the reflecting surface nor a high measurement cost, because this method equates the reflected sound produced by the reflecting surface to a series of radiated sounds from a simple source located below the reflecting surface. At the moment, the problem of a half-space sound field is converted into the problem of a multi-source free sound field, the surface acoustic impedance of a reflecting surface does not need to be considered, and only single-side sound pressure or particle vibration velocity is needed for measurement, so that the measurement cost is greatly reduced. This Method is called I-ESM (Independent-Equivalent Source Method) because it does not depend on the surface acoustic impedance of the reflecting surface and is based on the Equivalent Source Method. The reconstruction accuracy of the I-ESM half-space sound field depends to a great extent on the configuration of the equivalent sources, especially the series of equivalent sources that characterize the action of the reflecting surfaces. Thus, unreasonable equivalent source configurations may significantly degrade the half-space soundfield reconstruction accuracy of the I-ESM.
Therefore, the existing half-space sound field reconstruction method has three defects and shortcomings: (1) the measurement cost is high; (2) surface acoustic impedance dependent on the reflecting surface; (3) the reconstruction accuracy is not ideal.
Disclosure of Invention
The invention aims to provide a half-space sound field reconstruction method and device by utilizing a half-space near-field acoustic holography technology, which ensure the reconstruction precision of a half-space sound field by reasonably configuring an equivalent source, are independent of the surface acoustic impedance of a reflecting surface and have lower measurement cost.
The technical scheme adopted by the invention is as follows:
in one aspect, the present invention provides a half-space sound field reconstruction method, including:
configuring equivalent sources and virtual source surfaces according to the vibrating body and the boundary surface to obtain a plurality of equivalent source configuration schemes; the virtual source surface comprises a virtual source surface gamma where the vibrating body equivalent source is located and a virtual source surface omega where the boundary surface reflection action equivalent source is located;
respectively calculating sound pressure of a half-space sound field aiming at each equivalent source configuration scheme;
calculating a regular solution of source strong column vectors corresponding to each equivalent source configuration scheme based on the sound pressure of the half-space sound field;
reconstructing the surface normal vibration velocity of the vibrator corresponding to each equivalent source configuration scheme based on the regular solution of the source strong column vector;
calculating the reconstruction error of the surface normal vibration speed of the vibrating body of each equivalent source configuration scheme;
taking the equivalent source configuration scheme with the minimum reconstruction error of the normal vibration speed of the surface of the vibrator as a final equivalent source configuration scheme;
and reconstructing a half-space sound field by using the final equivalent source configuration scheme.
Optionally, the equivalent source configuration is performed according to the position and size of the virtual source surface and the distribution interval of the equivalent sources on the virtual source surface, so as to obtain a plurality of equivalent source configuration schemes.
Optionally, the vibrating body is spherical, and is defined as a spherical sound source S, and the equivalent source configuration includes:
configuring an imaginary source plane gamma as a spherical surface concentric with the spherical sound source S;
configuring the spherical radius of an imaginary source plane gamma;
configuring the distribution of a plurality of equivalent sources of the spherical sound source S on an imaginary source plane gamma;
configuring an imaginary source plane omega as a plane parallel to the reflecting surface;
the retreating distance of the virtual source surface omega relative to the reflecting surface is configured;
configuring the size of a virtual source surface omega;
the distribution of a plurality of equivalent sources characterizing the reflection of the reflecting surface over the imaginary source plane omega is configured.
As an embodiment, when the equivalent source is configured: a plurality of equivalent sources of the spherical sound source S are uniformly distributed on the virtual source plane gamma, and the discrete intervals of the azimuth angle and the polar angle of the equivalent sources on the virtual source plane gamma are pi/4 and pi/6; the size of the virtual source plane Ω is configured, that is, the coordinate range covered by the virtual source plane Ω on the abscissa and the ordinate is configured, and the distribution of the equivalent sources on the virtual source plane Ω is configured, that is, the interval between the equivalent sources in the directions of the abscissa and the ordinate is configured.
Optionally, the size of the virtual source plane Ω and the configuration of the equivalent source distribution are set by a parameter set (x)1,x2,y1,y2,dx,dy) Is represented by the formula (I) in which x1,x2Is the boundary value of the coordinate range covered by the imaginary source plane omega on the abscissa, y1,y2Is the boundary value of the coordinate range covered by the imaginary source plane omega on the ordinate, dx,dyThe discrete distances of the equivalent source on the imaginary source plane omega in the abscissa and ordinate directions.
Optionally, two groups of equivalent sources for characterizing the spherical sound source and the boundary reflection action are defined asAndwhereinAndthe source strengths of the ith and j equivalent sources respectively;
for any equivalent source configuration scheme, the matrix form of the sound pressure of the half-space sound field of all the measurement points on the holographic surface H is considered as follows:
wherein the content of the first and second substances,is a sound pressure transfer function matrix between sound pressure on a representation holographic surface H and an equivalent source on an imaginary source surface gamma,is a sound pressure transfer function matrix between sound pressure on a representation holographic surface H and an equivalent source on an imaginary source surface omega,is a complex acoustic pressure transfer function matrix, QΣIs the source intensity column vector of all equivalent sources, i represents the imaginary unit, ρ represents the air density, and ω represents the angular frequency.
Optionally, the source strong column vector QΣThe canonical solution of (a) is:
wherein, the superscript "H" represents the Hermite conjugate transpose, the superscript "-1" represents the matrix inversion, ε represents the regularization parameter, and E is the identity matrix.
Optionally, the normal vibration speed V of the surface of the vibrating bodySThe reconstruction is as follows:
wherein the content of the first and second substances,the vibration velocity transfer function matrix between the normal vibration velocity on the surface S of the vibration body and equivalent sources on virtual source surfaces gamma and omega is expressed as:
in the formula (I), the compound is shown in the specification,consisting of the following functions:
in the formula, gv,free() Representing the particle velocity transfer function, k is the wave number, ". represents the dot product operation, nSIs the unit normal vector of the surface of the vibrating body,is the nth node of the surface of the vibration bodyWith the ith equivalent source on the imaginary source plane gammaThe distance between the two or more of the two or more,is thatWith the j-th equivalent source on the virtual source plane omegaThe distance between them;representing equivalent sourcesTo surface node of vibration bodyLinear transfer method ofThe included angle between the direction of the vibrator and the normal direction of the surface of the vibrator,representing equivalent sourcesTo surface node of vibration bodyThe linear transmission direction of the vibrating body and the normal direction of the surface of the vibrating body form an included angle;are respectively expressed as
Optionally, for any equivalent source configuration scheme, the reconstruction error of the surface normal vibration speed of the vibrating body is as follows:
in the formula (I), the compound is shown in the specification,andrespectively is the reconstructed normal vibration speed and the theoretical normal vibration speed of the surface of the vibrator; the theoretical normal vibration velocity is expressed as:
in the formula, v0Is a uniform radial vibration velocity raIs the radius of the vibrating ball, zSIs the z coordinate of the surface node of the vibrating sphere, zaIs the z coordinate of the center of the sphere.
On the other hand, the invention also discloses a half-space sound field reconstruction device, which comprises:
the equivalent source configuration module is used for configuring equivalent sources and virtual source surfaces according to the vibrating body and the boundary surface to obtain a plurality of equivalent source configuration schemes; the virtual source surface comprises a virtual source surface gamma where the vibrating body equivalent source is located and a virtual source surface omega where the boundary surface reflection action equivalent source is located;
the source intensity column vector regular solution calculation module is used for calculating the regular solution of the source intensity column vector corresponding to each equivalent source configuration scheme based on the predicted sound pressure of the half-space sound field aiming at each equivalent source configuration scheme;
the vibrating body surface normal vibration velocity calculating module is used for reconstructing the vibrating body surface normal vibration velocity corresponding to each equivalent source configuration scheme based on the regular solution of the source strong column vector;
the reconstruction error calculation module is used for calculating the reconstruction errors of the surface normal vibration speeds of the vibrating bodies of the equivalent source configuration schemes;
the equivalent source configuration scheme selection module is used for taking the equivalent source configuration scheme with the minimum reconstruction error of the normal vibration velocity of the surface of the vibrating body as a final equivalent source configuration scheme;
and the half-space sound field reconstruction module is used for reconstructing the half-space sound field by utilizing the final equivalent source configuration scheme.
Advantageous effects
According to the method, equivalent source configuration is carried out on the basis of a half-space near-field acoustic holography technology I-ESM, the reconstruction error of the normal vibration speed of the surface of the vibrating body is taken as a reference, and the scheme with the minimum reconstruction error is selected from a plurality of equivalent source configuration schemes, so that the proper virtual source surface position, the virtual source surface size and the equivalent source distribution interval are determined, the half-space sound field is reconstructed, the influence of a reflecting surface on the half-space sound field can be more accurately represented, the reconstruction precision of the half-space sound field is improved, and the reconstruction precision of the half-space sound field is improved. Meanwhile, by utilizing the semi-space near-field acoustic holography technology, the semi-space sound field problem is converted into a multi-source free sound field problem, the surface acoustic impedance of a reflecting surface does not need to be considered, and only single-side sound pressure or particle vibration velocity is needed for measurement, so that the measurement cost can be greatly reduced.
Drawings
FIG. 1 is a schematic flow chart of the method of the present invention;
FIG. 2 is a schematic diagram of the relative positions of a spherical sound source S, a holographic surface H, virtual source surfaces Γ and Ω in three-dimensional space according to an embodiment of the method of the present invention;
fig. 3 is a plan view of a spherical sound source S, a holographic surface H, and an imaginary source surface Ω, and the size and equivalent source distribution interval of the imaginary source surface Ω in an embodiment of the method of the present invention, (a) a top view; (b) a side view;
FIG. 4 shows different equivalent source configurations (parameter set (x)) in an embodiment of the method of the present invention1,x2,y1,y2,dx,dy) And a receding distance hz) Under the condition of 500Hz, reconstructing errors of the normal vibration speed of the surface of the spherical sound source;
FIG. 5 is a diagram of the geometry of an imaginary source plane Ω in an embodiment of the method of the present invention, (a) a square; (b) a rectangle shape;
FIG. 6 shows the reconstructed result and theoretical value of the normal vibration velocity of the spherical sound source surface at 500Hz in the embodiment of the method of the present invention, (a) the real part; (b) x is a theoretical value; from parameter set number 15 and hz-0.001 m; from parameter set 1 and hz-0.2m of the obtained reconstruction;from parameter set No. 6 and hz-0.5m of the obtained reconstruction;
FIG. 7 is a spherical sound source surface normal vibration velocity reconstruction error frequency response curve in an embodiment of the method of the present invention;
FIG. 8 is a graph showing the variation of the reconstruction error of the normal vibration velocity of the surface of the spherical sound source with the flow resistance of the reflecting surface at 500Hz in the embodiment of the method of the present invention.
Detailed Description
The following further description is made in conjunction with the accompanying drawings and the specific embodiments.
Example 1
Referring to fig. 1, the half-space sound field reconstruction method of the present embodiment includes:
configuring equivalent sources and virtual source surfaces according to the vibrating body and the boundary surface to obtain a plurality of equivalent source configuration schemes; the virtual source surface comprises a virtual source surface gamma where the vibrating body equivalent source is located and a virtual source surface omega where the boundary surface reflection action equivalent source is located;
respectively calculating sound pressure of a half-space sound field aiming at each equivalent source configuration scheme;
calculating a regular solution of source strong column vectors corresponding to each equivalent source configuration scheme based on the sound pressure of the half-space sound field;
reconstructing the surface normal vibration velocity of the vibrator corresponding to each equivalent source configuration scheme based on the regular solution of the source strong column vector;
calculating the reconstruction error of the surface normal vibration speed of the vibrating body of each equivalent source configuration scheme;
taking the equivalent source configuration scheme with the minimum reconstruction error of the normal vibration speed of the surface of the vibrator as a final equivalent source configuration scheme;
and reconstructing a half-space sound field by using the final equivalent source configuration scheme.
In this embodiment, equivalent source configuration is performed according to the position and size of the virtual source surface and the distribution interval of the equivalent sources on the virtual source surface, so as to obtain a plurality of equivalent source configuration schemes.
If the vibrating body is spherical, defined as a spherical sound source S, the equivalent source configuration includes:
configuring an imaginary source plane gamma as a spherical surface concentric with the spherical sound source S;
configuring the spherical radius of an imaginary source plane gamma;
configuring the distribution of a plurality of equivalent sources of the spherical sound source S on an imaginary source plane gamma;
configuring an imaginary source plane omega as a plane parallel to the reflecting surface;
the retreating distance of the virtual source surface omega relative to the reflecting surface is configured;
configuring the size of a virtual source surface omega;
the distribution of a plurality of equivalent sources characterizing the reflection of the reflecting surface over the imaginary source plane omega is configured.
When the equivalent source is configured: a plurality of equivalent sources of the spherical sound source S are uniformly distributed on the virtual source plane gamma, and the discrete intervals of the azimuth angle and the polar angle of the equivalent sources on the virtual source plane gamma are pi/4 and pi/6; the size of the virtual source plane Ω is configured, that is, the coordinate range covered by the virtual source plane Ω on the abscissa and the ordinate is configured, and the distribution of the equivalent sources on the virtual source plane Ω is configured, that is, the interval between the equivalent sources in the directions of the abscissa and the ordinate is configured.
The size of the virtual source plane omega and the configuration of the equivalent source distribution are set by the parameter set (x)1,x2,y1,y2,dx,dy) Is represented by the formula (I) in which x1,x2Is the boundary value of the coordinate range covered by the imaginary source plane omega on the abscissa, y1,y2Is the boundary value of the coordinate range covered by the imaginary source plane omega on the ordinate, dx,dyThe discrete distances of the equivalent source on the imaginary source plane omega in the abscissa and ordinate directions.
Two groups of equivalent sources for representing the effects of spherical sound sources and boundary reflection are respectively defined asAndwhereinAndthe source strengths of the ith and j equivalent sources respectively;
for any equivalent source configuration scheme, the matrix form of the sound pressure of the half-space sound field of all the measurement points on the holographic surface H is considered as follows:
wherein the content of the first and second substances,is a sound pressure transfer function matrix between sound pressure on a representation holographic surface H and an equivalent source on an imaginary source surface gamma,is a sound pressure transfer function matrix between sound pressure on a representation holographic surface H and an equivalent source on an imaginary source surface omega,is a complex acoustic pressure transfer function matrix, QΣIs the source intensity column vector of all equivalent sources, i represents the imaginary unit, ρ represents the air density, and ω represents the angular frequency.
Source strong column vector QΣThe canonical solution of (a) is:
wherein, the superscript "H" represents the Hermite conjugate transpose, the superscript "-1" represents the matrix inversion, ε represents the regularization parameter, and E is the identity matrix.
Normal vibration speed V of surface of vibratorSThe reconstruction is as follows:
wherein the content of the first and second substances,the vibration velocity transfer function matrix between the normal vibration velocity on the surface S of the vibration body and equivalent sources on virtual source surfaces gamma and omega is expressed as:
in the formula (I), the compound is shown in the specification,consisting of the following functions:
in the formula, gv,free() Representing the particle velocity transfer function, k is the wave number, ". represents the dot product operation, nSIs the unit normal vector of the surface of the vibrating body,is the nth node of the surface of the vibration bodyWith the ith equivalent source on the imaginary source plane gammaThe distance between the two or more of the two or more,is thatWith the j-th equivalent source on the virtual source plane omegaThe distance between them;representing equivalent sourcesTo surface node of vibration bodyThe included angle between the straight line transmission direction and the normal direction of the surface of the vibrating body,representing equivalent sourcesTo surface node of vibration bodyThe linear transmission direction of the vibrating body and the normal direction of the surface of the vibrating body form an included angle;are respectively expressed as
For any equivalent source configuration scheme, the reconstruction error of the surface normal vibration speed of the vibrating body is as follows:
in the formula (I), the compound is shown in the specification,andrespectively the reconstructed normal vibration speed and theory of the surface of the vibratorNormal vibration speed; the theoretical normal vibration velocity is expressed as:
in the formula, v0Is a uniform radial vibration velocity raIs the radius of the vibrating ball, zSIs the z coordinate of the surface node of the vibrating sphere, zaIs the z coordinate of the center of the sphere.
Examples 1 to 2
Based on embodiment 1, in this embodiment, a spherical sound source S with a radius of 0.1m is located above a certain reflection surface as an example, and a half-space sound field is reconstructed.
A Cartesian rectangular coordinate system is established by taking the projection of the circle center of the spherical sound source S on the reflecting surface as an origin and the reflecting surface as an xOy plane, and the sound field with z larger than 0 is a half-space sound field to be researched. Assume that the spherical center of the spherical sound source S is 0.5m from the reflection surface, as shown in fig. 3 (b). The spherical sound source S is taken as a simulation object for research, and the method for reconstructing the half-space sound field comprises the following specific steps:
step A: two groups of equivalent sources representing the reflection action of the spherical sound source S and the boundary surface are respectively arranged on an imaginary source surface gamma and an imaginary source surface omega, which are respectively marked asAndwhereinAndthe source strengths of the ith and j equivalent sources, respectively. The virtual source plane gamma is a small spherical surface concentric with the spherical sound source S, the spherical radius is 0.02m, and the equivalent source Q isΓUniformly distributed over the virtual source plane Γ, at discrete intervals of π/4 and π/6, respectively, in azimuth and polar angles. The imaginary source plane omega is a plane parallel to the reflecting surface, as shown in FIG. 2, the equivalent source QΩIs prepared fromThe placement scheme may be considered from two aspects: (1) the position of the virtual source plane omega is set by a back distance h relative to the reflecting surfacezRepresents; (2) size of virtual source plane, equivalent source distribution interval, etc., in a parameter set (x)1,x2,y1,y2,dx,dy) As shown in fig. 3. Wherein the retreat distance hzSequentially setting the grain size to be-0.001 m, -0.2m, -0.5m and-1 m; parameter set (x)1,x2,y1,y2,dx,dy) There were 22 sets as shown in table 1.
Table 122 sets of equivalent source configuration parameters (x)1,x2,y1,y2,dx,dy)
And B: selecting an equivalent source QΓAnd QΩIn one configuration, the sound pressure at a certain point r on the holographic surface H can be expressed as:
where ρ is the air density, ω is the angular frequency,andthe position coordinates of the ith and the j equivalent sources in the three-dimensional space respectively. gfreeRepresenting the free space green's function, the sound pressure transfer function, can be expressed as:
wherein, k is a wave number,is the field point r and the equivalent source pointThe distance of (a) to (b),is the horizontal distance between the two.
Assuming that the hologram surface H has M measurement points, considering all the measurement points on the hologram surface H, equation (1) can be written in a matrix form:
in the formula (I), the compound is shown in the specification,is a sound pressure transfer function matrix between sound pressure on a representation holographic surface H and an equivalent source on an imaginary source surface gamma,is a sound pressure transfer function matrix between sound pressure on a representation holographic surface H and an equivalent source on an imaginary source surface omega,is a complex acoustic pressure transfer function matrix, QΣIs the source strong column vector of all equivalent sources.
In the present embodiment, the hologram surface H is located at a position where y is 0.2m, the measurement range is-0.25 m to 0.25m in the x direction, 0.25m to 0.75m in the z direction, and the measurement interval is 0.05 m. The holographic sound pressure data can be directly measured in practical application; if the numerical simulation calculation is carried out, the numerical simulation calculation is generally carried out by a boundary element method, and Gaussian white noise with the signal-to-noise ratio of 30dB is added.
And C: on condition that the number of measurement points is greater than the number of equivalent sources, i.e. M>I + J, based on holographic sound pressure PHSolving for the equivalent source QΣThe canonical solution of (c):
the upper mark in the formula: "H" represents the Hermite conjugate transpose, "-1" represents the matrix inversion operation, and epsilon is the regularization parameter; e is an identity matrix.
Step D: obtaining an equivalent source QΣAfter the regular solution, the normal vibration speed of the surface of the vibrating body can be reconstructed:
in the formula,is a vibration velocity transfer function matrix between the normal vibration velocity on the surface S of the vibration body and equivalent sources on virtual source surfaces gamma and omega,can be expressed as:
in the formula (I), the compound is shown in the specification,andrespectively consisting of the following functions:
wherein ". cndot." represents a dot product fortuneN is calculatedSIs the unit normal vector of the surface of the vibrating body,is the nth node of the surface of the vibration bodyAndthe distance between the two or more of the two or more,is thatAndthe distance between them.
Step E: calculating the reconstruction error of the surface normal vibration speed of the vibrating body:
in the formula (I), the compound is shown in the specification,andthe reconstructed normal vibration velocity and the theoretical normal vibration velocity of the surface of the vibrating body are respectively.Expressed as:
in the formula, v0Is a uniform radial vibration velocity raIs the radius of the vibrating ball,zSIs the z coordinate of the surface node of the vibrating sphere, zaIs the z coordinate of the center of the sphere. In numerical simulation, the theoretical normal vibration velocityThe theoretical normal vibration velocity can be obtained from the formula (10), and can be obtained through measurement in practical application.
Step F: sequentially selecting equivalent sources QΓAnd QΩAnd (e) repeating the steps b to e, analyzing and comparing the reconstruction errors of the normal vibration speed of the surface of the vibrator under the conditions of different configuration schemes, and searching for a smaller value, wherein the corresponding equivalent source configuration scheme is the more appropriate equivalent source configuration scheme in the half-space sound field.
FIG. 4 shows the spherical sound source surface normal vibration velocity reconstruction error at 500Hz under different equivalent source configurations in the embodiment of the method of the present invention.
First, the retreat distance h is analyzedz. At hzUnder the conditions of sequentially taking the values of-0.001 m, -0.2m and-0.5 m, the parameter group (x)1,x2,y1,y2,dx,dy) When the values are the same, the reconstruction error of the normal vibration velocity follows hzIs reduced. But when h iszWhen the value is smaller-1 m, the reconstruction error is not reduced any more, but sometimes increased. As a result, a receding distance h of-0.5 m was obtainedzIt is a more ideal choice. Interestingly, the spherical sound source S is located just 0.5m above the reflecting surface. Therefore, the back-off distance of the imaginary source plane Ω with respect to the reflecting surface should be comparable to the distance of the sound source above the reflecting surface in order to obtain better half-space sound field reconstruction results.
Next, the size (x) of the virtual source plane Ω is analyzed1,x2,y1,y2) And an equivalent source distribution interval (d)x,dy). When h is generatedzWhen the values are-0.001 m, -0.2m, -0.5m, especially when the first two values are taken, each normal vibration velocity reconstruction error curve has the same turning point, such as No. 3 and No. 17. With reference to Table 1, these turning points are exactly the size (x) of the virtual source plane Ω1,x2,y1,y2) Changed situation. In addition, when the magnitude of the virtual source plane Ω is the same, the reconstruction error is spaced with the equivalent source distribution (d)x,dy) The variation is not large. Therefore, the size of the virtual source plane omega has a relatively obvious influence on the reconstruction accuracy, and the equivalent source distribution interval has a very small influence on the reconstruction accuracy. But when h iszWhen the value is-1 m, that is, when the virtual source plane Ω is far from the reflecting surface, the reconstruction accuracy is hardly affected by the size or the equivalent source distribution interval. In view of the above analysis results, to simplify the analysis process, only the equivalent source distribution interval (d) is analyzed belowx,dy) All 0.05 m.
Then, the special points are analyzed. When h is generatedz0.001m or hzWhen the normal vibration velocity is equal to-0.2 m, the reconstruction error of the normal vibration velocity is respectively in the parameter group (x)1,x2,y1,y2,dx,dy) The minimum value and the maximum value are taken for the 9 th and the 15 th. With reference to table 1 and fig. 5, the virtual source plane Ω 9 determined by the parameter set No. 9 exactly covers the area between the sound source and the hologram plane, and the virtual source plane Ω 15 determined by the parameter set No. 15 is the largest virtual source plane covering the area determined by all the parameter sets. These analysis results show that in the case where the virtual source plane is relatively close to the reflection plane, such as-0.001 m and-0.2 m, the equivalent source should be arranged in the region between the sound source and the hologram plane.
Finally, the best equivalent source configuration is found. From the above analysis, the retreat distance hzShould be set to-0.5 m, but if the parameter set (x)1,x2,y1,y2,dx,dy) When the selection is improper, the error of the normal vibration velocity reconstruction may be slightly larger, sometimes even larger than h under the condition of the same parameter groupzTake the reconstruction error at-1 m, say # 15. As can be seen from FIG. 4, at hzIn the case of-0.5 m, when the parameter set is No. 3, No. 6, No. 9, No. 11, or No. 20, the reconstruction error is small. As can be seen from fig. 5(a), Ω 3 exactly covers the projection of the spherical sound source on the virtual source plane Ω; omega 6 is slightly smaller, and equivalent sources are all focused on the projection of the central part of the spherical sound source on omega; omega 20 also covers the projection of the central part of the spherical sound source on omega. On the other hand, Ω 9 just covers soundThe region between the source and the holographic surface, Ω 11, although slightly larger, covers this region too, and in any case, in order to obtain a better reconstruction result, the virtual source surface Ω should cover either the projection of the central part of the spherical sound source on Ω or the region between the sound source and the holographic surface, and the virtual source surface should not be oversized.
Based on the above analysis, table 2 gives 3 representative equivalent source configurations.
TABLE 2 equivalent source configuration scheme and corresponding normal vibration velocity reconstruction error
Wherein, the 15 th parameter group (x)1,x2,y1,y2,dx,dy) And hz-0.001m represents a poor solution, parameter set No. 6 and hz-0.5m represents a better solution, while parameter set No. 1 and hzA value of-0.2 m is neither too good nor too bad. The spherical sound source surface normal vibration velocity is reconstructed by respectively adopting 3 equivalent source configuration schemes, and the reconstruction result is shown in fig. 6. As can be seen from the figure, the sum h is given by parameter set No. 6zThe reconstruction results obtained at-0.5 m fit very well with the theoretical values, and are given by the parameter set No. 15 and hzThe reconstruction results obtained at-0.001 m deviate considerably from the theoretical values. In addition, table 2 also shows the reconstruction error of the normal vibration velocity in the case of three equivalent source configurations. It can be easily found thatzThe reconstruction error obtained for-0.5 m is small, and is given by parameter set No. 15 and hzThe reconstruction error obtained is much larger at-0.001 m. These analysis results show parameter set No. 6 and hzThe equivalent source configuration scheme is relatively suitable, and the I-ESM is an effective high-precision half-space sound field reconstruction method as long as the equivalent source configuration is reasonable.
In addition, fig. 7 and 8 show the variation curves of the spherical sound source surface normal vibration velocity reconstruction error along with the frequency and the flow resistance of the reflecting surface respectively. As can be seen from the figure, the sum of the parameter set No. 6 and the parameter set hzReconstruction error obtained at-0.5 mThe difference is always small, and is composed of parameter set No. 15 and hzThe reconstruction error obtained is much larger at-0.001 m, and parameter set No. 6 and h will be explained againzAn ideal equivalent source configuration scheme is-0.5 m, and a suitable equivalent source configuration scheme can provide higher and more stable half-space sound field reconstruction accuracy for I-ESM.
In summary, the analysis results of the examples fully illustrate that: (1) the invention can provide a proper equivalent source configuration scheme that the retreat distance of the virtual source surface omega relative to the reflecting surface is equivalent to the distance of the sound source above the reflecting surface, and omega covers the projection of the central part of the spherical sound source on omega or the area between the sound source and the holographic surface, and the size is not suitable to be overlarge; (2) the appropriate equivalent source configuration scheme obtained by the method can ensure the accuracy of the semi-space near-field acoustic holography technology I-ESM which does not depend on the surface impedance of the reflecting surface and has low measurement cost, provides higher and more stable semi-space sound field reconstruction precision for the I-ESM, and verifies the beneficial effects of the method.
Example 2
Based on the same inventive concept as the embodiment, the embodiment is a half-space sound field reconstruction apparatus, including:
the equivalent source configuration module is used for configuring equivalent sources and virtual source surfaces according to the vibrating body and the boundary surface to obtain a plurality of equivalent source configuration schemes; the virtual source surface comprises a virtual source surface gamma where the vibrating body equivalent source is located and a virtual source surface omega where the boundary surface reflection action equivalent source is located;
the source intensity column vector regular solution calculation module is used for calculating the regular solution of the source intensity column vector corresponding to each equivalent source configuration scheme based on the predicted sound pressure of the half-space sound field aiming at each equivalent source configuration scheme;
the vibrating body surface normal vibration velocity calculating module is used for reconstructing the vibrating body surface normal vibration velocity corresponding to each equivalent source configuration scheme based on the regular solution of the source strong column vector;
the reconstruction error calculation module is used for calculating the reconstruction errors of the surface normal vibration speeds of the vibrating bodies of the equivalent source configuration schemes;
the equivalent source configuration scheme selection module is used for taking the equivalent source configuration scheme with the minimum reconstruction error of the normal vibration velocity of the surface of the vibrating body as a final equivalent source configuration scheme;
and the half-space sound field reconstruction module is used for reconstructing the half-space sound field by utilizing the final equivalent source configuration scheme.
The specific functions of the above modules are implemented with reference to embodiment 1.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While the present invention has been described with reference to the embodiments shown in the drawings, the present invention is not limited to the embodiments, which are illustrative and not restrictive, and it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (10)
1. A half-space sound field reconstruction method is characterized by comprising the following steps:
configuring equivalent sources and virtual source surfaces according to the vibrating body and the boundary surface to obtain a plurality of equivalent source configuration schemes; the virtual source surface comprises a virtual source surface gamma where the vibrating body equivalent source is located and a virtual source surface omega where the boundary surface reflection action equivalent source is located;
aiming at each equivalent source configuration scheme, respectively calculating a regular solution of a source strong column vector corresponding to each equivalent source configuration scheme based on the predicted sound pressure of the half-space sound field;
reconstructing the surface normal vibration velocity of the vibrator corresponding to each equivalent source configuration scheme based on the regular solution of the source strong column vector;
calculating the reconstruction error of the surface normal vibration speed of the vibrating body of each equivalent source configuration scheme;
taking the equivalent source configuration scheme with the minimum reconstruction error of the normal vibration speed of the surface of the vibrator as a final equivalent source configuration scheme;
and reconstructing a half-space sound field by using the final equivalent source configuration scheme.
2. The reconstruction method of a half-space sound field according to claim 1, wherein equivalent source configuration is performed according to the position and size of the virtual source surface and the distribution interval of the equivalent sources on the virtual source surface to obtain a plurality of equivalent source configuration schemes.
3. A half-space sound field reconstruction method according to claim 1 or 2, wherein the vibrating body is spherical, and defined as a spherical sound source S, and the equivalent source configuration comprises:
configuring an imaginary source plane gamma as a spherical surface concentric with the spherical sound source S;
configuring the spherical radius of an imaginary source plane gamma;
configuring the distribution of a plurality of equivalent sources of the spherical sound source S on an imaginary source plane gamma;
configuring an imaginary source plane omega as a plane parallel to the reflecting surface;
the retreating distance of the virtual source surface omega relative to the reflecting surface is configured;
configuring the size of a virtual source surface omega;
the distribution of a plurality of equivalent sources characterizing the reflection of the reflecting surface over the imaginary source plane omega is configured.
4. A half-space sound field reconstruction method according to claim 3, wherein when the equivalent source is configured: a plurality of equivalent sources of the spherical sound source S are uniformly distributed on the virtual source plane gamma, and the discrete intervals of the azimuth angle and the polar angle of the equivalent sources on the virtual source plane gamma are pi/4 and pi/6; the size of the virtual source plane Ω is configured, that is, the coordinate range covered by the virtual source plane Ω on the abscissa and the ordinate is configured, and the distribution of the equivalent sources on the virtual source plane Ω is configured, that is, the interval between the equivalent sources in the directions of the abscissa and the ordinate is configured.
5. A reconstruction method of a half-space sound field according to claim 4, characterized in that the size of the virtual source plane Ω and the configuration of the equivalent source distribution are set by the parameter set (x)1,x2,y1,y2,dx,dy) Is represented by the formula (I) in which x1,x2Is the boundary value of the coordinate range covered by the imaginary source plane omega on the abscissa, y1,y2Is the boundary value of the coordinate range covered by the imaginary source plane omega on the ordinate, dx,dyThe discrete distances of the equivalent source on the imaginary source plane omega in the abscissa and ordinate directions.
6. A half-space sound field reconstruction method as claimed in claim 1, wherein two sets of equivalent sources characterizing spherical sound sources and boundary reflection are defined asAndwhereinAndthe source strengths of the ith and j equivalent sources respectively;
for any equivalent source configuration scheme, the matrix form of the sound pressure of the half-space sound field of all the measurement points on the holographic surface H is considered as follows:
wherein the content of the first and second substances,is a sound pressure transfer function matrix between sound pressure on a representation holographic surface H and an equivalent source on an imaginary source surface gamma,is a sound pressure transfer function matrix between sound pressure on a representation holographic surface H and an equivalent source on an imaginary source surface omega,is a complex acoustic pressure transfer function matrix, QΣIs the source intensity column vector of all equivalent sources, i represents the imaginary unit, ρ represents the air density, and ω represents the angular frequency.
7. The method of claim 6, wherein the source enhancement vector Q isΣThe canonical solution of (a) is:
wherein, the superscript "H" represents the Hermite conjugate transpose, the superscript "-1" represents the matrix inversion, ε represents the regularization parameter, and E is the identity matrix.
8. The half-space sound field reconstruction method of claim 7, wherein the surface normal velocity V of the oscillating bodySThe reconstruction is as follows:
wherein the content of the first and second substances,the vibration velocity transfer function matrix between the normal vibration velocity on the surface S of the vibration body and equivalent sources on virtual source surfaces gamma and omega is expressed as:
in the formula (I), the compound is shown in the specification,consisting of the following functions:
in the formula, gv,free() Representing the particle velocity transfer function, k is the wave number, ". represents the dot product operation, nSIs the unit normal vector of the surface of the vibrating body,is the nth node of the surface of the vibration bodyWith the ith equivalent source on the imaginary source plane gammaThe distance between the two or more of the two or more,is thatWith the j-th equivalent source on the virtual source plane omegaThe distance between them;representing equivalent sourcesTo surface node of vibration bodyThe included angle between the straight line transmission direction and the normal direction of the surface of the vibrating body,representing equivalent sourcesTo surface node of vibration bodyThe linear transmission direction of the vibrating body and the normal direction of the surface of the vibrating body form an included angle;are respectively expressed as
9. The reconstruction method of the half-space sound field according to the claim 1 or 8, wherein for any equivalent source configuration scheme, the reconstruction error of the normal vibration speed of the surface of the vibrating body is as follows:
in the formula (I), the compound is shown in the specification,andrespectively is the reconstructed normal vibration speed and the theoretical normal vibration speed of the surface of the vibrator; the theoretical normal vibration velocity is expressed as:
in the formula, v0Is a uniform radial vibration velocity raIs the radius of the vibrating ball, zSIs the z coordinate of the surface node of the vibrating sphere, zaIs the z coordinate of the center of the sphere.
10. A half-space sound field reconstruction device is characterized by comprising:
the equivalent source configuration module is used for configuring equivalent sources and virtual source surfaces according to the vibrating body and the boundary surface to obtain a plurality of equivalent source configuration schemes; the virtual source surface comprises a virtual source surface gamma where the vibrating body equivalent source is located and a virtual source surface omega where the boundary surface reflection action equivalent source is located;
the source intensity column vector regular solution calculation module is used for calculating the regular solution of the source intensity column vector corresponding to each equivalent source configuration scheme based on the predicted sound pressure of the half-space sound field aiming at each equivalent source configuration scheme;
the vibrating body surface normal vibration velocity calculating module is used for reconstructing the vibrating body surface normal vibration velocity corresponding to each equivalent source configuration scheme based on the regular solution of the source strong column vector;
the reconstruction error calculation module is used for calculating the reconstruction errors of the surface normal vibration speeds of the vibrating bodies of the equivalent source configuration schemes;
the equivalent source configuration scheme selection module is used for taking the equivalent source configuration scheme with the minimum reconstruction error of the normal vibration velocity of the surface of the vibrating body as a final equivalent source configuration scheme;
and the half-space sound field reconstruction module is used for reconstructing the half-space sound field by utilizing the final equivalent source configuration scheme.
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